The present invention relates to a processing reactor and, more particularly, to a processing reactor for the thermal processing and chemical deposition of thin film applications on a substrate, such as semiconductor wafer, in which the injection of gas into the chamber can be controlled to provide better control of the substrate processing.
In semiconductor fabrication, gases are injected in the chamber in order to deposit thin films on the substrate. Typically, the substrate is heated during the deposition process and during various other temperature activated processes for example, oxide growth, etching, and thermal annealing. The control of the deposition depends on the control of the gas flow and dynamic pressure, and the wafer temperature. Uniform wafer temperatures provide uniform process variables on the substrate; for instance in film deposition, if the temperature in one region of the substrate varies from another region, the thickness of the deposition in these regions may not be equal. Moreover, the adhesion of the deposition to the substrate may vary as well. Furthermore, if the temperature in one region of the substrate is higher or lower than the temperature in another region of the substrate, a temperature gradient within the substrate material is formed. This temperature gradient produces thermal moments in the substrates which in turn induce radial local thermal stresses in the substrate. These local thermal stresses can reduce the substrate""s strength and, furthermore, damage the substrate. Uniform heating, however, has been recently achieved by a new and improved heater assembly disclosed in U.S. Pat. No. 5,951,896 issued Sep. 14, 1999, and commonly assigned to Micro C Technologies, Inc. of Grand Rapids, Mich., the disclosure of which is herein incorporated by reference in its entirety.
In addition to temperature uniformity, the uniformity of film deposition is affected by the uniformity of the delivery of the process gas. Good process uniformity usually requires adjustments and optimizations for both the wafer temperature uniformity and the gas flow pattern of the process gas. In most conventional chambers or reactors, the reactant gas is delivered through a single port, which injects gas into the chamber above the wafer. Due to the geometry of the wafer, the resulting deposition of the gas onto the wafer is not uniform.
In order to provide improved delivery of the gas, shower-like gas injection systems have been developed in which separate gases are injected in a shower-like pattern over the entire substrate area. However, such gas delivery systems fill the entire chamber volume and, thus, deposit films on the chamber walls in addition to the substrate. Other solutions have included injecting gas radially inward to the substrate across circular contoured plates positioned adjacent the substrate, for example as disclosed in U.S. Pat. No. 4,834,022, the disclosure of which is herein incorporated by reference in its entirety. However, this inward radial injection system provides less control of the gas injection over larger substrates. With the increase in size of the substrates which are now being manufactured, this radial injection system is not as effective.
More recently, an improved gas delivery system (disclosed in U.S. Pat. No. 5,814,365, commonly assigned to Micro C Technologies, Inc. of Grand Rapids, Mich., the disclosure of which is hereby incorporate by reference in its entirety) has been developed which directs one or gases onto a discrete area of the substrate, which better controls the gas delivery onto the substrate. With increased control of gas delivery, however, it is believed that further optimizations can be achieved by better controlling the dynamic pressure in the processing chamber.
Consequently, there is a need for a processing reactor which can deliver and direct the flow of reactant gas or gases onto the substrate during processing in a uniform manner and, further, achieve even greater control over the gas flow within the reactor""s processing chamber so that the film or films deposited on the substrate have a substantially uniform thickness across the device side of the substrate.
According to the present invention, a reactor for processing semiconductor substrates includes a gas injection system that injects gas in a manner to form a film or films on the substrate that have more uniform thickness, especially on larger substrates on the order of up to 300 mm or greater.
In one form of the invention, a reactor includes a reactor housing defining a processing chamber and an improved gas injection system. The reactor further includes a platform which is rotatably supported in the reactor housing for rotatably supporting the substrate in the processing chamber. The gas injection assembly is adapted to inject at least one gas into the processing chamber and onto the substrate when the platform rotates the substrate. The gas injection assembly has a substrate facing surface, which is adapted to vary the dynamic pressure in the processing chamber to vary the processing time of the substrate in the processing chamber.
In one aspect, the substrate facing surface is repositionable in the processing chamber to vary the dynamic pressure in the processing chamber. For example, the gas injection assembly may include a gas injection manifold, which includes the substrate facing surface. Preferably, the gas injection manifold is movably mounted in the housing to vary the dynamic pressure in the processing chamber.
In other aspects, the substrate facing surface includes at least one angled portion with respect to the platform, with the angled portion varying the dynamic pressure in the processing chamber. Furthermore, the substrate facing surface may include a second angled portion. In preferred form the angled portions are joined to form an apex. The apex is preferably centrally aligned over the substrate.
In yet another aspect, the gas injection assembly includes at least one port for injecting a first gas into the processing chamber. The port is preferably located in the substrate facing surface and, further, is centrally located in the substrate facing surface. In further aspects, the gas injection assembly includes a second port for injecting a second gas into the processing chamber. For example, the first port and the second port may be coaxial.
According to another form of the invention, a processing reactor for processing a semiconductor substrate includes a housing and a platform rotatably supported in a processing chamber defined in the housing for rotatably supporting the substrate in the processing chamber of the reactor. The reactor further includes a heater and a gas manifold. The gas manifold includes a substrate facing surface and at least one injection port for injecting gas axially onto the substrate. The substrate facing surface is adapted to vary the dynamic pressure in the processing chamber to vary the processing time for the substrate.
In one aspect, the substrate facing surface is repositionable in the processing chamber to vary the dynamic pressure in the processing chamber. Preferably, the substrate facing surface includes first and second portions, with at least one of the first and second portions being angled with respect to the platform.
In other aspects, the housing includes a cover. The gas manifold is supported in the cover and preferably removably supported in the cover to permit repositioning of the substrate facing surface relative to the platform. In further aspects, the substrate facing surface includes first and second portions that are angled to form a positive wedge-shaped substrate facing surface, preferably a positive rectilinear wedge-shaped surface. Alternately, the first and second angled portions are angled to form a negative rectilinear wedge-shaped substrate facing surface.
According to yet another form of the invention, a processing reactor for processing a semiconductor substrate includes a reactor housing, a heater housing rotatably supported in the reactor housing, and a platform supported on the heater housing for rotatably supporting the substrate in the processing chamber of the reactor. A heater is positioned in the heater housing and is adapted to heat the substrate. The reactor further includes a gas manifold that has a substrate facing surface and at least one gas injection port for injecting gas axially onto the substrate through the substrate facing surface, with the substrate facing surface being adapted to vary the dynamic pressure in the processing chamber to vary the processing time for the substrate.
In other aspects, the gas manifold is supported in a gas injection assembly housing, which supports the gas manifold in the reactor housing. The gas injection assembly housing includes a transverse passage, with the gas manifold being positioned and supported in the transverse passage. Preferably, the gas manifold is movably supported in the transverse passage.
In yet other aspects, the gas injection assembly housing further supports a gas exhaust manifold for exhausting gases from the processing chamber. Preferably, the gas exhaust manifold extends around the gas injection manifold to isolate gas injected through the gas injection port on a discrete area of the substrate.
As will be understood, the reactor of the present invention provides numerous advantages over prior known reactors. The reactor provides a gas injection system which directs one or more reactant gases to the substrate during processing in a controlled manner and directs the gas or gases to discrete regions of the substrate under controlled dynamic pressures so that the film or films deposited on the substrate are more uniform.
These and other objects, advantages, purposes and features of the invention will be apparent to one skilled in the art from a study of the following description taken in conjunction with the drawings.